This invention generally relates to a sampling device. More particularly, the invention relates to a secondary sampling device for particulate matter.
Many industries process large quantities of raw materials or products in particulate form. Frequently, the quality or value of such material is determined by a physical or chemical analysis of a very small sample. For instance, it is not uncommon to base the quality of a large quantity, such as a railroad car full, of such material on the analysis of a few hundred grams or less of the material. Obviously, very small errors in the analysis can have profound effects on decisions regarding the value or acceptability of the material. A critical step in providing an accurate analysis of such material is to obtain a representative sample.
A sample is usually taken from a feed stream of material in free fall as it passes through a relatively large pipe or chute. Since particulate matter may segregate as it passes through a pipe or chute, for instance, because of differences in particle size or particle density, it is advantageous to obtain a representative sample across the entire cross-section of the sample stream. Obtaining such a sample is the function of a primary sampling device.
Primary sampling devices are commercially available in a variety of designs. They usually include a sample cutter which continuously moves across the product stream at a uniform speed, thereby collecting a representative portion of the entire stream. Although the primary sampler may take only a small portion of the product stream, the amount taken may, nevertheless, be too large for an analysis. In such case, a representative sample must be taken from the material collected by the primary sampler. The equipment used to take such a sample is generally referred to as the secondary sampler.
Secondary samplers are also available in a variety of designs. Generally, secondary samplers, like primary samplers, comprise a moving sample cutter which moves through the product stream from the primary sampler. Although many of such samplers are very effective in obtaining good representative samples, they are usually comprised of motors, gears and other moving parts which increase costs and maintenance expenses.